PRISTIPHORA-ABIETINA (HYM, TENTHREDINIDAE) - A BIOINDICATOR FOR AIR-POLLUTION - PECULIARITIES OF IMMATURE SPRUCE NEEDLES AS LARVAL FOOD

Some needle parameters (water content, fiber, sugar, starch, nitrogen, tannins) important for the nutritional quality for the larvae of the small spruce sawfly Pristiphora abietina (Christ) were determined to e xplain the partial mass outbreak of this insect in the Hausruck (Upper Austria). The stands chosen for investigation - comparable in microcl imate and coincidence, but with different infestation rates - were exp osed to variable air contaminants. The trees seriously attacked by the insect - even though exposed to higher nitrogen impact - showed signi ficantly lower nitrogen levels, lower water content, sugar and starch levels, but increased fiber and tannin concentrations. Shoot length al so was significantly reduced. We suppose that the excessive air pollut ion in the area investigated is responsible for these changes in needl e chemistry, enhanced by the counteractions of the heavily attacked tr ees against the insect pest.